Not sure what’s wrong...

I’m 25 years old. I’ve missed 2 periods now, been 60 days since my last actual period. (I’ve always been regular) anyhow, I’ve been super tired lately, and no other symptoms, but today, I’ve been having constant cramps all day. I’ve never spotted, I’ve only had milky looking discharge. I have taken over 10 pregnancy tests, 4 different brands, all negative. I took a blood test, also negative. Anyone else had symptoms like this and been pregnant??

I’m going to my OB this Monday to get checked out, but I’m super nervous. My sister has ovarian cancer, and I’m wondering if maybe I have the same thing? Except, she would have lots of periods, and I’m having opposite symptoms.